Hot top



R. W. CARTER July 22, 1958 NVENTR.' ROBERT u'. CAR TER, WM/7M@ lHEL. E-

HOT TOP Filed Aug. 5, 1956 TTS-1 his Attorney.

United states Patent o Hor ToP Robert W. Carter, Library, Pa., assignorto United States This invention relates to a hot top and is directedprimarily to that type of hot top which has a cast steel shell linedwith refractory. The hot tops of this type in common use use insulatingrefractory which is provided With a protective lining of a water mixedparting compound applied to a minimum thickness of 1/2 in. Such hot topsand linings are shown in Urmetz Patent No. 2,046,043, dated June 30,1936, and Peterson Patent No. 2,678,481, dated May 18, 1954. After theparting compound has dried the hot top is placed on the ingot mold andthe molten steel poured therein. Before the hot top can be used again anew lining of the parting compound must be applied and dried. Thisoperation is laborious, time-consuming and expensive. The average lifeof the hot top before relining with insulating material is approximately35 pours. The reason for the short number of pours is that theinsulating material is eroded by the molten metal in spite of the slightprotection of the parting compound.

It is an object of my invention to provide an improved hot top or aprotective lining therefor wherein the life of the hot top beforerelining is greatly increased.

Another object is to provide such a hot top which enables the volume ofmolten metal contained therein to be reduced with a correspondingincreased yield from the ingot.

These and other objects will be more apparent after referring to thefollowing specification and attached drawings, in which:

Figure 1 is a vertical section through the preferred embodiment of myinvention;

Figure 2 is a sectional view taken on the line II-II of Figure l;

Figure 3 is a View of the mold of Figure l showing an intermediate stagein its manufacture; and

Figure 4 is a view similar to Figure 1 showing a modification of myinvention.

Referring more particularly to the drawings, the reference numeral 2indicates a tubular shell preferably made of cast steel. A sand ring 4is attached to the bottom of the shell 2. Both the shell 2 and sand ring4 are standard in this type of hot top as shown by the above mentionedpatents and no invention is claimed in so far as these two parts areconcerned. Special types of sand rings are shown in Charman Patents Nos.1,956,894 and 1,956,895, both dated May 1, 1934. A lining of insulationis provided on the inner surface of the shell.` This lining 6 may be aninsulating block of a commercial type having a base of vermiculite,diatomaceous earth, mineral wood or silicate-gel. The block may bemolded or pressed from these materials or combinations thereof and maybe burned or unburned. They have a high insulating value, thecoefficient of thermal conductivity K being not more than 1.2 B., t.u./sq. ft./F./in. thick/hr. Insulating tire brick may also be used thesebeing mixtures of clay and saw dust or other combustible which burns outleaving a porous clay brick. The insulating value is less than forblock, K generally being between 2 and 3.

The blocks will stand temperatures between 1200-2000 F. and theinsulating brick will stand temperatures of between 1600 and 3000 F. Ahigh temperature air setting cement coating 8 is applied over the lining6. This cement is a clay or clay/alumina base mortar containing sodiumsilicate or other air setting bonds to provide cold` setting or airsetting properties. A castable refractory lining 10 is placed on top ofthe cement coating 8. This is Ia calcined lireclay or fireclaygrog/alumina product which when tempered with water will developstructural strength by reason of a hydraulic set as provided by calciumaluminate cements such as that sold under the trademark Lumnite. A thinlayer of parting compound 12 is arranged on the refractory lining 10.This parting compound is an air setting sand mixture generallycontaining some carbonaceous material.

In making the hot top the inner surface of the shell 2 is lined withinsulating lire brick or insulating block 6 and a thin layerapproximately 1A; in. thick of a high temperature air setting cement isapplied thereto.. A form F is then placed on the mold in any suitablemanner as shown in Figure 3. The high temperature castable refractorylining 10 is placed between the mold F and the cement lining 6. Thecement acts: as a bond between the layers 6 and 10 and also as a seal toprevent water from the layer 10 getting into the insulating layer 6. Itwill be noted that the inner surface of the coating 12 is tapered for apurpose which will appear later. The surface of the form F is well oiledto facilitate removal of the form. One or two hours after the refractorycastable lining has been poured a plurality of vent holes 14,

twelve of which are shown7 are pierced in the: top portion of thecastable refractory lining to permit moisture to escape during drying.The form F is removed eight hours yafter pouring of the refractory, thisbeing facilitated by the taper in the lining 12. After the form isremoved the hot top is permitted to air set for about four hours afterwhich it is heated to remove the moisture.

When the hot top is to be used on an ingot mold the sand ring 4, whichis a molded ring pressed with an air setting bonded material and dried,is placed on the mold in the usual manner .and the parting compound 12having a thickness of about la in. is put in place and dried. Thecoating of parting compound is destroyed during the cast but it is onlynecessary to replace the sand seal 4 and coating 12 before the hot topis ready for another pour. The life of the lining proper is greatlyincreased over that of the old type and in many instances over pourshave been made in one hot top before the lining proper is replaced.Since the layer of parting compound is much thinner than in the formerhot tops the time required to dry the same is much less.. The castablerefractory lining 10 protects the insulating layer 6, thus permittingthe longer life. The insulating material prevents loss of heat so thatthe volume of molten steel in the hot top can be reduced. While it ispreferred to cast the castable refractory lining 10 in place it ispossible to pre-cast the refractory into block or bricks and lay them inplace.

Figure 4 shows another modication of my hot top which has some of theadvantages of my preferred embodiment. In this embodiment a monolithiclining 16 of a castable refractory of the type described above is caston the inner surface of the tubular shell 2 and a thin coating 18 ofparting compound corresponding to the coating 12 is placed thereon.

While two embodiments of my invention have been shown and described itwill be apparent that other adaptations and modifications may be madewithout departing from the scope of the following claims.

I claim:

l. A hot top comprising a tubular shell, a lining of insulation on theinner surface of said shell, a coating of high temperature air settingmoisture resistant cement on said insulation, and a high temperaturecastable refractory monolithic lining on said coating.

2. A hot top comprising a tubular shell, a lining of insnlotion on theinner surface of said shell, a coating of mh temperature air settingmoisture resistant cement on said insulation, a high temperaturecastable refractory monolithic lining on said cement, and a thin coatingof a parting compound on said refractory lining.

3. A hot tolga` comprising a tubular shell, a lining of insulation onthe inner surface of said shell, a high temperature moisture resistantseal coating on said insulation, and a high temperature castablerefractory monolithic lining on said coating.

References Cited in the lle of this patent UNITED STATES PATENTS 710,588Knox Oct. 7, 1902 1,837,146 Brooks Dec. 15, 1931 10 1,982,490 Williamset al. Nov. 27, 1934 2,293,089 Wajner -1, Aug, 18, 1942 FOREIGN PATENTS708,599 Great Britain May 5, 1954

